The purpose of this project is to study the possible deleterious effects of multiple transfusion, and has been designed to examine the clinical and subclinical effects of multiple transfusion upon pulmonary function and gas exchange. The specific aims are 1) to correlate changes in gas exchange with number and size of microaggregates infused during blood transfusion, and concurrently describe the time course, severity and permanence of these changes; 2) to assess the significance of these changes in patients with heaalthy lungs compared to patients with pre-existing pulmonary compromise; 3) to further define this significance in an animal model of smoke inhalation with varying degrees of pulmonary compromise by direct infusions of microaggregates with known number and size; 4) to further define the technique for counting microaggregates in vivo and subsequently to apply these techniques to an in vivo animal model investigating the pulmonary consequences of endogenously created microemboli following soft tissue trauma; and 5) to assess the role of soft tissue trauma in the development of pulmonary dysfunction by comparing pulmonary defects in patients with penetrating and blunt trauma who have comparable doses of infused microaggregates. These aims will be achieved by applying techniques available to this institution including 1) accurate and complete data collection and analysis; 2) standard pulmonary function and gas exchange testing; 3) multiple inert gas elimination technique for sensitive gas exchange analysis, and highly specialized laser methods of microaggregate sizing andcounting both ex vivo and in vivo. The objectives of this project involve a multidisciplinary approach (surgery, nuclear engineering and physiology) in an effort to dissect the causes of pulmonary failure associated with remote and direct mechanical injury, thermal injury and sepsis.